Listener Sensitivity Research Articles

Woody Guthrie, American Radical

Woody Guthrie, American Radical

Effects of listener bias on auditory acuity for aircraft in real-world ambient environments

Hoglund et al. (2010) investigated the ability of listeners to detect the presence of aircraft masked by ongoing ambient sounds using a two interval forced choice (2IFC) procedure. They found that the signal-to-noise ratio required for target detection varied across the different types of ambient environments. Recordings of helicopters in flight were used as target signals and maskers were recorded in rural, suburban and urban locations. Their goal was to better approximate real-world conditions. The goal of the current study is to extend those results to include factors that may bias the listener under more realistic conditions. The 2IFC procedure is designed to minimize listener bias; however, real-world listening conditions are more typically one interval situations. The frequency of occurrence of aircraft over-flights and the costs of errors and rewards for correct responses may substantially affect some estimates of listener sensitivity. Work reported here investigated the influence of apriori probability of target occurrence and manipulation of the pay-off matrix on the acuity measures reported by Hoglund, et al., using the same target sounds and environmental maskers. Psychometric functions shifted by ~18 dB as frequency of targets varied from 20% to 80%. ROC curves display the influence of pay-off manipulations.

Cross-linguistic perception of Itunyoso Trique tone

Recent findings have argued in favor of the categorical perception of tonal contrasts in Taiwanese Mandarin and Standard Mandarin (Hallé, Chang, & Best, 2004; Xu, Gandour, & Francis, 2006), and most recently in Mandarin and Cantonese (Peng et al., 2010). Findings in favor of the categorical perception of tone emerge most clearly from cross-linguistic work on speech perception. The current study continues this line of research by investigating the categorical perception of Itunyoso Trique tone among Trique and French listeners. Tonal stimuli were presented to listeners in an AXB discrimination task (2AFC) and an AXB identification task (2AFC), closely following methods used in Hallé et al. (2004). Evidence for a listener sensitivity to tonal categories was found for Trique listeners in their discrimination performance, but this pattern did not correspond to the identification performance. Overall, French speakers performed better overall at tone discrimination than Trique listeners, who largely ignored within-category phonetic differences. Both Trique and French listeners were found to be sensitive to psychoacoustic differences between stimuli, though French speakers relied more heavily on such differences. The findings here argue for the importance of both phonetic and auditory memory for the perception of Trique lexical tone.

Suppressed Alpha Oscillations Predict Intelligibility of Speech and its Acoustic Details

Modulations of human alpha oscillations (8-13 Hz) accompany many cognitive processes, but their functional role in auditory perception has proven elusive: Do oscillatory dynamics of alpha reflect acoustic details of the speech signal and are they indicative of comprehension success? Acoustically presented words were degraded in acoustic envelope and spectrum in an orthogonal design, and electroencephalogram responses in the frequency domain were analyzed in 24 participants, who rated word comprehensibility after each trial. First, the alpha power suppression during and after a degraded word depended monotonically on spectral and, to a lesser extent, envelope detail. The magnitude of this alpha suppression exhibited an additional and independent influence on later comprehension ratings. Second, source localization of alpha suppression yielded superior parietal, prefrontal, as well as anterior temporal brain areas. Third, multivariate classification of the time-frequency pattern across participants showed that patterns of late posterior alpha power allowed best for above-chance classification of word intelligibility. Results suggest that both magnitude and topography of late alpha suppression in response to single words can indicate a listener's sensitivity to acoustic features and the ability to comprehend speech under adverse listening conditions.

All representations are not equal: Differential activation of words and phonological variants across accents

Given the massive variation in natural speech, how listeners recognize words is a central issue for linguistic theory. Listener sensitivity to acoustic fluctuations in speech has provided us with one piece of the puzzle: detailed, specific representations. We provide another piece: differential activation of these representations. We conducted a semantic priming with General American listeners of positively viewed non-rhotic British English accents and negatively viewed non-rhotic New York City accents (slender'THIN; slend-UH(BE)'THIN; slend-UH(NYC)'THIN). Controlling participant experience and self-reported familiarity with both accents, only the words produced in a British accent primed semantically related targets. There is no a priori reason to expect this pattern, as the phonological variant and lexical items are controlled. We suggest that two variants equally experienced in number (raw frequency) are perceived differentially because positive and negative attitudes influence the activation lexical representations. Additionally, by examining particular participant groups from non-rhotic regions, we show an oscillation between effects of raw frequency and listener attitudes. This work (1) provides a broader understanding of factors influencing activation, (2) increases our understanding of how frequency effects are modulated by other factors (subjective listener attitudes), and (3) illuminates the interactive nature of linguistic and social factors in speech perception.

Perception of long-distance coarticulation: An event-related potential and behavioral study

ABSTRACTIn this study we explore listeners' sensitivity to vowel to vowel (VV) coarticulation, using both event-related potential (ERP) and behavioral methodologies. The stimuli used were vowels “colored” by the coarticulatory influence of other vowels across one, three or five intervening segments. The paradigm used in the ERP portion of the study was intended to elicit the mismatch-negativity (MMN) component, a negative deflection typically seen at central midline scalp sites about 200 ms after the presentation of a “deviant” acoustic stimulus occurring among a train of “standard” acoustic stimuli. VV coarticulation at near and medium distances was associated with significant MMN-like effects, which however were not observed in response to the longest distance coarticulatory contrasts. Subjects' ERP results did not predict their performance on the behavioral task, which found evidence of listener sensitivity to even the furthest distance coarticulatory effects. Although the MMN has previously been shown to be sensitive to phonemic contrasts, this is the first study using ERP methodology to investigate the subphonemic processing associated with the perception of coarticulation.

Perceptual distinctiveness of vowels in relation to dialectal sound change.

We examine distinctiveness among four vowels /ɪ, ε, æ, a/ in Appalachian English in the perception of children (9–13 years) and adults (50–65 years) who spoke the same local variety as the talkers who produced the stimuli. Each listener responded to unique exemplars of bids, beds, bads, bides (both stressed and unstressed) produced by 40 talkers, male and female, children (8–12 years) and adults (50–65 years). The highest identification rates were for beds, and the lowest for bides. For each vowel, stressed variants yielded slightly higher rates than unstressed. Examination of confusions among spectral neighbors revealed systematic confusions between bids and beds. Confusions for bads and bides varied as a function of talker age, gender, and listener age, reflecting effects of cross-generational sound change in this dialect. In a second task, the vowels were presented in hVd-frame and stimulus uncertainty was elevated by increasing the number of vowel categories (12), talker age groups (3), and the addition of another dialect. Similar pattern of responses was obtained by different listeners (children and adults) but overall identification rates were comparatively higher. Altogether, these results show listener sensitivity to cross-generational sound change, which affects both vowel position and formant dynamics. [Work supported by NIH.]

Age effects in discrimination of repeating sequence intervals

The study measured listener sensitivity to increments in the inter-onset intervals (IOIs) of successive 20-ms 4000-Hz tone bursts in isochronous sequences. The stimulus sequences contained two-six tone bursts, separated equally by silent intervals, with tonal IOIs ranging from 25 to 100 ms. Difference limens (DLs) for increments of the tonal IOIs were measured to assess listener sensitivity to changes of sequence rate. Comparative DLs were also measured for increments of a single interval located within six-tone isochronous sequences with different tone rates. Listeners included younger normal-hearing adults and two groups of older adults with and without high-frequency sensorineural hearing loss. The results, expressed as Weber fractions (DL/IOI), revealed that discrimination improved as the sequence tone rate decreased and the number of tonal components increased. Discrimination of a single sequence interval also improved as the number of sequence components increased from two to six but only for brief intervals and fast sequence rates. Discrimination performance of the older listeners with and without hearing loss was equivalent and significantly poorer than that of the younger listeners. The discrimination results are examined and discussed within the context of multiple-look mechanisms and possible age-related differences in the sensory coding of signal onsets.

Characteristics of listener sensitivity to talker-specific phonetic detail

Previous research shows that listeners are sensitive to talker differences in phonetic properties of speech, including voice-onset-time (VOT) in word-initial voiceless stop consonants, and that learning how a talker produces one voiceless stop transfers to another word with the same voiceless stop [Allen, J. S., and Miller, J. L. (2004). J. Acoust. Soc. Am. 115, 3171-3183]. The present experiments examined whether transfer extends to words that begin with different voiceless stops. During training, listeners heard two talkers produce a given voiceless-initial word (e.g., pain). VOTs were manipulated such that one talker produced the voiceless stop with relatively short VOTs and the other with relatively long VOTs. At test, listeners heard a short- and long-VOT variant of the same word (e.g., pain) or a word beginning with a different voiceless stop (e.g., cane or coal), and were asked to select which of the two VOT variants was most representative of a given talker. In all conditions, which variant was selected at test was in line with listeners' exposure during training, and the effect was equally strong for the novel word and the training word. These findings suggest that accommodating talker-specific phonetic detail does not require exposure to each individual phonetic segment.

Discrimination of repetitive intervals by younger and older listeners.

The study measured listener sensitivity to increments in the inter-onset intervals (IOIs) separating successive 20-ms 4000-Hz tone bursts in isochronous sequences. Stimulus sequences contained from 2–6 tone bursts, separated equally by IOIs in the range of 25–100 ms across stimulus conditions. Difference limens (DLs) for increments of all tonal IOIs were measured to assess listener sensitivity to changes in sequence rate. A DL was also measured for increments of a single IOI located at a fixed position within 6-tone sequences. Listeners included younger and older normal-hearing adults and older adults with high-frequency hearing loss. The results revealed that the relative DLs for sequence rate decreased as the magnitude of the reference IOI and the number of sequence components increased. The relative DL for a single interval embedded within a six-tone sequence was smaller than corresponding DLs measured with two-tone sequences, but only for brief reference IOIs. The discrimination performance of the older listeners was poorer than that of the younger listeners, especially for two-tone sequences with the shortest reference IOIs. The findings are interpreted within the context of multiple-look mechanisms and possible age-related differences in the sensory coding of signal onsets. [Research supported by the National Institute on Aging, NIH.]

Age-related differences in discrimination of temporal intervals in accented tone sequences

The study measured listener sensitivity to increments of a target inter-onset interval (IOI) embedded within isochronous tone sequences that featured a single accented tonal component. The sequences consisted of six 1000-Hz tone bursts separated by silent intervals to establish equal tonal IOIs of 200 ms within the sequence. Tone burst durations within the sequences were 50 ms, except one tone had a longer duration of 100 ms to produce a perception of accent. Duration DLs in ms for increments of a single sequence IOI were measured adaptively by adjusting the duration of the silent interval between two tones. Sequence position of the target IOI differed across conditions. Listeners included young normal-hearing adults and older adults with and without hearing loss. Discrimination performance of the two older listener groups was equivalent and significantly poorer than that of the younger listeners in each discrimination condition. The age-related discrimination deficits were independent of sequence locations of both the target interval and the accented tonal component. Comparative DLs collected for target intervals in unaccented tone sequences with equal tone durations revealed that the detrimental effects of accent on temporal discrimination were primarily restricted to the older listeners.

Characteristics of listener sensitivity to talker-specific phonetic detail.

Listeners are sensitive to talker differences in phonetic properties of speech, including voice-onset-time (VOT) in word-initial stop consonants. Earlier findings from our laboratory [R. M. Theodore and J. L. Miller, J. Acoust. Soc. Am. 123, 3934 (2008)] indicate that learning how a talker produces one voiceless stop (e.g., /p/ in pain) transfers to another voiceless stop (e.g., /k/ in cane), providing support for feature-based processing of VOT at the level of individual talkers. Here we examined possible constraints on such processing by asking whether transfer would also occur when the learning and transfer words were not minimal pairs. In familiarization phases, listeners heard two talkers produce pain. Critically, word-initial VOTs were manipulated such that one talker produced pain with relatively short VOTs and the other talker produced pain with relatively long VOTs. In test phases, listeners were presented with a short-VOT and a long-VOT variant of coal produced by each talker, and were asked to select which variant was most representative of the talker. Results showed that the listeners selected the VOT variant of coal in line with their previous exposure to pain, indicating that feature-based processing of talker-specific VOT is robust.

Temporal weighting of interaural level differences in high‐rate click trains

When high‐carrier‐frequency stimuli are amplitude modulated at rates above 200 Hz, lateralization based on envelope interaural time differences (ITD) becomes dominated by onset ITD. The role of onset cues in interaural‐level‐difference (ILD) processing, however, is less well understood. Although theoretical predictions suggest that onset dominance should have similar effects upon ILD as upon ITD, some experimental data suggest that ILD processing retains greater sensitivity during post‐onset segments of a high‐rate stimulus. In this study, subjects lateralized ILDs carried by trains of 16 Gaussian‐filtered clicks (carrier frequency 4000 Hz) that varied in interclick interval (ICI) from 2 to 10 ms (modulation rate 100‐500 Hz). ILDs of individual clicks in each train were randomly perturbed. Multiple linear regression of listener responses onto the perturbed ILD values was used to generate temporal weighting functions (TWFs) that describe how a listener's sensitivity to ILD changes over the stimulus durati...

Age-related differences in discrimination of an interval separating onsets of successive tone bursts as a function of interval duration

The study measured listener sensitivity to increments in the inter-onset interval (IOI) separating pairs of successive 20-ms 4000-Hz tone pulses. A silent interval between the tone pulses was adjusted across conditions to create reference tonal IOI values of 25-600 ms. For each condition, a duration DL for increments of the tonal IOI was measured in listeners comprised of young normal-hearing adults and two groups of older adults with and without high-frequency hearing loss. Discrimination performance of all listeners was poorest for the shorter reference IOIs, and improved to stable levels for longer reference intervals exceeding about 200 ms. Temporal sensitivity of the young listeners was significantly better than that of the elderly listeners in each condition, with the largest age-related differences observed for the shortest reference interval. Age-related differences were also observed for duration DLs measured using single 4000-Hz tone bursts set to three reference durations in the range 50-200 ms. The tone DLs of all listeners were smaller than the corresponding tone-pair IOI DLs, particularly for the shorter reference stimulus durations. There were no significant performance differences observed between the older listeners with and without hearing loss for either discrimination task.

Localizing noise in rooms via steady‐state interaural time differences

Noise lateralization experiments with headphones show that the steady‐state interaural time difference (ITD) is, or is not, a valuable cue for sound lateralization depending on the height of the peak of the interaural cross‐correlation function (cc). To discover whether these headphone results could be extended to the localization of sound in rooms, binaural recordings were made of one‐third‐octave noises in diverse environments: a dry classroom, a laboratory, and a reverberation room. Sound sources and a KEMAR recording manikin were moved about in each room to vary the cc from 0.2 to 0.8. The recordings, with ITDs digitally controlled, were presented to five listeners by headphones to measure listener sensitivity to ITD variations. It was found that sensitivity was almost entirely a function of cc with little weight attached to the actual room environment. ITD thresholds decreased monotonically with increasing cc. In agreement with earlier headphone studies using computed noises instead of room recordings, typical thresholds were higher by a factor of about 6 for a 2800‐Hz band where envelope ITD is used compared to a 700‐Hz band where waveform ITD is used. [Work supported by the NIDCD.]

Listener sensitivity to intensity variation in vowels in coarticulatory context

There are two sources of acoustic variation in the relative formant amplitude of a vowel which are unrelated to emphasis-oriented changes in articulatory effort: (1) vowel-specific intrinsic formant frequency pattern, which differs across vowel categories, and (2) the vowel’s immediate phonetic (coarticulatory) context. Listener sensitivity to the latter source of variation is examined here to establish the extent to which distortion in the distribution of acoustic energy across the vowel spectrum affects the perception of vowel quality. Synthetic versions of CVC syllables in symmetrical consonant environments were created (using stops or fricatives differing in place-of-articulation and voicing). Formant frequencies and amplitude values were modeled after those found in a large corpus of CVC acoustic data [E. Jacewicz and R. A. Fox, J. Acoust. Soc. Am. 117, 2623 (2005)]. Initial amplitude values for the first four formants in synthetic CVCs reflected the intensity distribution (and spectral tilt) typical of a vowel coarticulated with these consonants. Subsequent stepwise adjustments to selected formant levels were made to create a range of permissible and not permissible formant amplitude variations in coarticulatory context. Preliminary results indicate that listeners are sensitive to amplitude variation across vowel spectrum as a function of a specific consonant environment. [Work supported by NIDCD R03 DC005560-01.]

Listener sensitivity to variations in the relative amplitude of vowel formants

Listener sensitivity to formant amplitude variations in the perception of both within- and between-vowel-category differences was examined for two isolated synthetic vowels, /i/ and /ɪ/. The relative amplitudes of F2 and F4 were varied in steps along acoustic continua which were created in accord with formant amplitude patterns found in natural speech. The results showed that vowel-specific patterns of formant amplitude variation affected listeners’ judgments of “naturalness” of each vowel token, as well as its phonetic quality.

Listener sensitivity to individual talker differences in voice-onset-time.

Recent findings in the domains of word and talker recognition reveal that listeners use previous experience with an individual talker's voice to facilitate subsequent perceptual processing of that talker's speech. These findings raise the possibility that listeners are sensitive to talker-specific acoustic-phonetic properties. The present study tested this possibility directly by examining listeners' sensitivity to talker differences in the voice-onset-time (VOT) associated with a word-initial voiceless stop consonant. Listeners were trained on the speech of two talkers. Speech synthesis was used to manipulate the VOTs of these talkers so that one had short VOTs and the other had long VOTs (counterbalanced across listeners). The results of two experiments using a paired-comparison task revealed that, when presented with a short- versus long-VOT variant of a given talker's speech, listeners could select the variant consistent with their experience of that talker's speech during training. This was true when listeners were tested on the same word heard during training and when they were tested on a different word spoken by the same talker, indicating that listeners generalized talker-specific VOT information to a novel word. Such sensitivity to talker-specific acoustic-phonetic properties may subserve at least in part listeners' capacity to benefit from talker-specific experience.

Binaural specialisation in human auditory cortex: an fMRI investigation of interaural correlation sensitivity

A listener's sensitivity to the interaural correlation (IAC) of sound plays an important role in several phenomena in binaural hearing. Although IAC has been examined extensively in neurophysiological studies in animals and in psychophysical studies in humans, little is known about the neural basis of sensitivity to IAC in humans. The present study employed functional magnetic resonance imaging to measure blood oxygen level-dependent (BOLD) activity in auditory brainstem and cortical structures in human listeners during presentation of band-pass noise stimuli between which IAC was varied systematically. The stimuli evoked significant bilateral activation in the inferior colliculus, medial geniculate body, and auditory cortex. There was a significant positive relationship between BOLD activity and IAC which was confined to a distinct subregion of primary auditory cortex located bilaterally at the lateral extent of Heschl's gyrus. Comparison with published anatomical data indicated that this area may also be cytoarchitecturally distinct. Larger differences in activation were found between levels of IAC near unity than between levels near zero. This response pattern is qualitatively compatible with previous measures of psychophysical and neurophysiological sensitivity to IAC.

Difference limens for vocal aperiodicities

Although jitter, shimmer, and noise characterize all voice signals, recent data from a method of adjustment task suggest that these acoustic attributes do not all have equal perceptual importance. Listeners did not agree well with one another when asked to match the amounts of jitter or shimmer in a voice, although they did agree well in their matching responses to noise. Several explanations for this finding are possible. Listeners may be insensitive to differences in amounts of jitter and shimmer in a voice, so that difference limens are large relative to customary measurement resolution; or listeners may have difficulty separating jitter and shimmer perceptually from the composite noise component. To investigate these issues, we synthesized several series of stimuli with and without noise, and differing by steps in the amounts of jitter or shimmer present. Listeners heard pairs of these stimuli and were asked to respond whether stimuli were the same or different. Receiver operating characteristic analysis was applied to determine how listener sensitivity to jitter and shimmer varies. [Research supported by NIDCD.]